Slowly Removing Surface Ligand by Aging the Sample Enhances the Stability of Pd Nanosheets toward Electron Beam Irradiation and Electrocatalysis

Surface ligands play an important role in shape‐controlled growth and stabilization of colloidal nanocrystals. Their quick removal tends to cause structural deformation and/or aggregation to the nanocrystals. Herein, we demonstrate that the surface ligand based on poly(vinylpyrrolidone) (PVP) can be slowly removed from Pd nanosheets (NSs, 0.93 ± 0.17 nm in thickness) by simply aging the colloidal suspension. The aged Pd NSs show well‐preserved morphology, together with significantly enhanced stability toward both electron beam (e‐beam) irradiation and electrocatalysis (e.g., for the ethanol oxidation reaction). It is revealed that the slow desorption of PVP during aging forces the re‐exposed Pd atoms to reorganize, facilitating the surface to transform from being nearly perfect to defect‐rich. The resultant Pd NSs with abundant defects no longer rely on surface ligand to stabilize the atomic arrangement and thus show excellent structural and electrochemical stability. This work provides a facile and effective method to maintain the integrity of colloidal nanocrystals by slowly removing the surface ligand.